Apparatus and methods for delivery of multiple distributed stents

ABSTRACT

Blood vessels and other body lumens are stented using multiple, discreet stent structures. Stent structures may be balloon expandable or self-expanding and are delivered by a delivery catheter which is repositioned to spaced-apart delivery sights. By coating the stents with particular biologically active substances, hyperplasia within and between the implanted stents can be inhibited. An exemplary delivery catheter comprises a catheter body having both a pusher rod for advancing the stents relative to a sheath and a reciprocatable delivery catheter for implanting the stents.

CROSS-REFERENCES TO RELATED APPLICATIONS

The present application is a continuation of U.S. application Ser. No.11/685,339 (Attorney Docket No. 021629-000323US), filed Mar. 13, 2007,which is a divisional of U.S. patent application Ser. No. 10/306,813(Attorney Docket No. 021629-000320US), filed Nov. 27, 2002, which is anon-provisional of U.S. Patent Application Ser. No. 60/336,967 (AttorneyDocket No. 021629-000300) filed Dec. 3, 2001, and is also anon-provisional of U.S. Patent Application Ser. No. 60/364,389 (AttorneyDocket No. 021629-000310) filed on Mar. 13, 2002, the full disclosuresof which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to medical devices and methods.More particularly, the present invention relates to apparatus andmethods for independently delivering a plurality of luminal prostheseswithin a body lumen, such as a blood vessel.

Coronary artery disease is the leading cause of death and morbidity inthe United States and Western society. In particular, atherosclerosis inthe coronary arteries can cause myocardial infarction, commonly referredto as a heart attack, which can be immediately fatal or, even ifsurvived, can cause damage to the heart which can incapacitate thepatient.

While coronary artery bypass surgery can be an effective treatment forstenosed arteries resulting from atherosclerosis or other causes, it isa highly invasive, costly procedure, which typically requiressubstantial hospital and recovery time. Percutaneous transluminalcoronary angioplasty, commonly referred to as balloon angioplasty, isless invasive, less traumatic, and significantly less expensive thanbypass surgery. Heretofore, however, balloon angioplasty has not beenconsidered as effective a treatment as bypass surgery. The effectivenessof balloon angioplasty, however, has improved significantly with theintroduction of stenting which involves the placement of a scaffoldstructure within the artery which has been treated by balloonangioplasty. The stent inhibits abrupt reclosure of the artery and hassome benefit in inhibiting subsequent restenosis resulting fromhyperplasia. Recently, experimental trials have demonstrated that thecoating of stents using anti-proliferative drugs, such as paclitaxel,can significantly reduce the occurrence of hyperplasia in angioplastytreated coronary arteries which have been stented with the coatedstents.

While the combination of balloon angioplasty with drug-coated stentsholds great promise, significant challenges still remain. Of particularinterest to the present invention, the treatment of extended ordisseminated disease within an artery remains problematic. Most stentshave a fixed length, typically in the range from 10 mm to 30 mm, and theplacement of multiple stents to treat disease over a longer lengthrequires the suggestive use of balloon stent delivery catheters.Moreover, it can be difficult to stent an angioplasty-treated region ofa blood vessel with the optimum stent length.

For these reasons, it would be desirable to provide improved stents,stent delivery systems, stenting methods, and the like, for thetreatment of patients having coronary artery disease, as well as otherocclusive diseases of the vasculature. In particular, it would bedesirable to provide stents, delivery systems, and methods for thetreatment of disseminated and variable length stenotic regions withinthe vasculature. For example, it would be desirable to provide apractical method which permits a physician to optimize the length of thetreated vessel which is stented according to the nature of the disease.More specifically, it would be desirable to provide apparatus, systems,and methods for facilitating the delivery of multiple stents and otherprostheses to blood vessels or other target body lumens. Such apparatus,systems, and methods should be suitable for delivery of individualstents or prostheses having very short lengths, typically as short as 3mm or shorter, at multiple contiguous and non-contiguous locationswithin a body lumen for optimized treatment thereof. At least some ofthese objectives will be met by the inventions described hereinafter.

2. Description of the Background Art

U.S. Pat. No. 6,258,117 B1 describes a stent having multiple sectionsconnected by separable or frangible connecting regions. Optionally, theconnecting regions are severed after the stent structure has beenimplanted in the blood vessel. U.S. Pat. Nos. 5,571,086; 5,776,141; and6,143,016 describe an expandable sleeve for placement over a ballooncatheter for the delivery of one or two stent structures to thevasculature. U.S. Pat. No. 5,697,948 describes a catheter for deliveringstents covered by a sheath.

BRIEF SUMMARY OF THE INVENTION

The present invention provides methods and apparatus for prosthesisplacement, such as stenting of body lumens, typically blood vessels, andmore typically coronary arteries. The methods and systems will also findsignificant use in the peripheral vasculature, the cerebral vasculature,and in other ducts, such as the biliary duct, the fallopian tubes, andthe like. The terms “stent” and “stenting” are defined to include any ofthe wide variety of expandable prostheses and scaffolds which aredesigned to be intraluminally introduced to a treatment site andexpanded in situ to apply a radially outward force against the innerwall of the body lumen at that site. Stents and prostheses commonlycomprise an open lattice structure, typically formed from a malleable orelastic metal. When formed from a malleable metal, the stents willtypically be expanded by a balloon which causes plastic deformation ofthe lattice so that it remains opened after deployment. When formed froman elastic metal, including super elastic metals such as nickel-titaniumalloys, the lattice structures will usually be radially constrained whendelivered and deployed by releasing the structures from such radialconstraint so that they “self-expand” at the target site. When the stentor lattice structures are covered with a fabric or polymeric membranecovering, they are commonly referred to as grafts. Grafts may be usedfor the treatment of aneurysms or other conditions which requireplacement of a non-permeable or semi-permeable barrier at the treatmentsite. The terms “prosthesis” and “prostheses” refer broadly to allradially expansible stents, grafts, and other scaffold-like structureswhich are intended for deployment within body lumens.

The stents and prostheses of the present invention may have any of avariety of common constructions, including helical structures,counterwound helical structures, expandable diamond structures,serpentine structures, or the like. Such conventional stent structuresare well described in the patent and medical literature. Specificexamples of suitable stent structures are described in the followingU.S. patents, the full disclosures of which are incorporated herein byreference: U.S. Pat. Nos. 6,315,794; 5,980,552; 5,836,964; 5,527,354;5,421,955; 4,886,062; and 4,776,337, the full disclosures of which areincorporated herein by reference. Preferred structures are describedherein with reference to FIGS. 4 and 5.

According to the present invention, the stents which are deployed mayhave a length of 1 mm or greater, usually 2 mm or greater, and typicallyof 3 mm or greater, usually being in the range from 1 mm to 100 mm,typically from 2 mm to 50 mm, more typically from 2 mm to 25 mm, andusually from 3 mm to 20 mm. The use of such short stent lengths isadvantageous since multiple stents are to be employed.

The methods and apparatus of the present invention will provide for thedeployment of a plurality of stents or other prostheses, usuallyincluding at least two stents, from a common stent delivery catheter.Usually, the number of delivered stents will be in the range from 2 to50, typically from 3 to 30, and most typically from 5 to 25. As morestents are placed on the delivery catheter, the individual stent lengthwill often be somewhat less, although this is not necessarily the casein all instances. The multiple prostheses may be deployed individuallyor in groups of two or more at single or multiple spaced-apart locationsin the body lumen or lumens.

In a first aspect of the present invention, a method for stenting anextended length of a body lumen comprises introducing a cathetercarrying a plurality of, usually at least two, discrete stents to thebody lumen. Usually, the introduction is percutaneous and, in the caseof intravascular delivery, uses a conventional introduction technique,such as the Seldinger technique. After reaching a target location, atleast a first stent is released from the catheter at that firstlocation. The catheter is then repositioned to a second location, and atleast a second stent is released from the catheter at the secondlocation. The catheter is then repositioned to a third location, and atleast a third stent is released from the catheter at the third location

In addition to deploying stents and other prostheses at spaced-apartlocations within a blood vessel or other body lumen, the methods andapparatus in the present invention can be used for delivering one, two,three, or more discrete stents or other prosthetic segments contiguouslyat a single location within the body lumen. In this way, the length ofthe prosthesis which is implanted can be selected and modified toaccommodate the length of the vessel to be treated. It will beappreciated that with systems which carry 10, 20, 30 or more quite shortprostheses or prosthesis segments, the length of the lumen being treatedcan be tailored very closely from very short to very long with theselectable intervals depending on the length of the prosthesis orprosthesis segment.

The deployment steps can, of course, be repeated a sufficient number oftimes so that all or at least most of the stents carried by the deliverycatheter are delivered to and deployed within the body lumen. Aparticular advantage of this delivery method is that the discrete stentsmay be distributed along extended lengths of the body lumen, typicallyin the range from 1 cm to 2 cm, often in the range from 1 cm to 5 cm,and in many instances even longer. Additionally, the stents may bedelivered so as to avoid side branches or other regions where placementof the stent is undesirable. Moreover, with the use of drug-coatedstents, it may be possible to place the stents apart by discretedistances, typically from one-half to one millimeter (mm), while stillachieving vessel patency and hyperplasia inhibition.

Releasing of the stents from the catheter may be achieved using aballoon to cause balloon expansion of the stent. Alternatively, releaseof the stent may be achieved by radially constraining an elastic orself-expanding stent within a lumen of the delivery catheter andselectively advancing the stent from the catheter and/or retracting thecatheter from over the stent. In one embodiment, a sheath over thestents includes a valve member, or “stent valve,” which allows stents tobe separated so that a balloon can more accurately inflate deployedstents while other stents remain within the sheath.

In preferred embodiments, the stents are coated with at least one agent,such as an agent which inhibits hyperplasia. The agent may bebiologically active or inert. Particular biologically active agentsinclude anti-neoplastic drugs such as paclitaxel, methotrexate, andbatimastal; antibiotics such as doxycycline, tetracycline, rapamycin,and actinomycin; immunosuppressant such as dexamethosone, methylprednisolone, nitric oxide sources such as nitroprussides; estrogen;estradiols; and the like. Biologically inert agents include polyethyleneglycol (PEG), collagen, polyglycolic acids (PGA), ceramic material,titanium, gold and the like.

In another aspect, the present invention comprises catheters andapparatus for stenting extended lengths of a body lumen, particularly ablood vessel. The catheters comprise a catheter body having a proximalend and a distal end. At least two discrete stents are carried at ornear a distal end of the catheter body. By “discrete,” it is meant thatthe stents are unconnected and can be deployed from the catheter in anunattached manner. (The delivery of attached prostheses is describedbelow.) Deployment of such discrete stents permits the individual stentsto be placed at spaced-apart target locations or immediately adjacentlywithin the blood vessel or other body lumen. The catheters furthercomprise deployment means for deploying the individual stents from thecatheter body. For example, the deployment means may comprise one ormore balloons for placement and radial expansion of the stents.Alternatively, the deployment means may comprise a pusher or otherdevice for advancing self-expanding stents from the distal end of thecatheter body and/or a sheath for selectively retracting over the stentsto permit self-expansion. In exemplary embodiments, the catheters willcarry at least two discrete stents, at least five discrete stents, andas many as 10 discrete stents, or in some cases, as many as 30 or morediscrete stents.

In a particular embodiment, the catheter comprises a single balloonwhich is reciprocatively mounted within the catheter body and adaptedfor receiving individual stents thereover. A pusher or other device forsuccessively and controllably loading individual or multiple stents overthe balloon is also provided. In this way, the catheter may carrymultiple stents and employ the single balloon for positioning andexpansion of the stents.

In further embodiments, the stents of the present invention are composedat least partly of a bioabsorbable material, such as polyethylene glycol(PEG), collagen, gelatin, polyglycolic acids (PGA), polylactic acids(PLA), and the like. Optionally, one or more bioactive substances aredispersed in the bioabsorbable material such that the bioactivesubstance will be released over time as the bioabsorbable materialdegrades. In a particular embodiment, the bioabsorbable material isformed on or within a scaffold composed on a non-bioabsorbable material,typically stainless steel, Nitinol™, or other conventional stent metalmaterial. Other materials, such as gold (e.g., pure or nearly puregold), platinum, or the like, may also be used.

In a further aspect of the present invention, a catheter for deliveringa plurality of expansible prostheses to a body lumen comprises acatheter body, a sheath, and a plurality of radially expansibleprostheses. The catheter body has a proximal end and a distal end, andthe sheath is coaxially disposed over the catheter body with theprostheses positionable in an annular space between the inside of thesheath and the exterior of the catheter body. The sheath is preferablyretractable relative to the catheter body so that the prostheses may beadvanced beyond a distal end of the sheath. Usually, the catheter willfurther comprise a pusher tube disposed coaxially over the catheter bodyand within an interior lumen of the sheath. A distal end of the pushertube will engage a proximal end of the proximal-most prosthesis so thatthe pusher tube can be distally advanced relative to the sheath toselectively push or deploy individual prostheses from the sheath. Often,such deployment is achieved by holding the pusher tube and prosthesessubstantially stationary relative to the body lumen while the sheath isretracted proximally to release or deploy the prostheses. Each of thepusher tube, sheath and catheter body may have a lubricious innersurface and/or a lubricious outer surface.

Usually, at least a distal portion of the sheath will have a greatercolumn strength than that of a distal portion of the catheter body.Additionally or alternatively, the pusher tube may also have a greatercolumn strength than a distal portion of a catheter body. By providingcolumn strength in the outer most portion of the catheter, i.e., thesheath, and optionally the pusher tube, the overall column strength ofthe catheter can be increased with a minimum increase in its diameter orprofile. It will be appreciated that low profile catheters are highlyadvantageous for accessing remote regions of the vasculature,particularly the small coronary and cerebral arteries. Using thepreferred constructions of the present invention, catheters havingdiameters 2 mm or less, and in some instances as low as 1 mm or less,can be achieved. The constructions will, of course, also be suitable forlarger diameter catheters for use in the peripheral and other largerblood vessels.

The catheter of the present invention will preferably carry at least twoprostheses, more preferably carrying at least three prostheses, andoften carrying a greater number of prostheses as set forth above inconnection with other embodiments. The prostheses will typically bearranged in an end-to-end manner either with or without a physicallinkage therebetween. The physical linkage may comprise a frangiblecomponent which must be mechanically broken or alternatively maycomprise a pair of coupling elements which fit together and which may beseparated without any material breakage. Frangible coupling elementswill usually comprise a strut, bar, spring, or similar connecting linkand will optionally be scored, notched, or otherwise adapted to breakalong a particular line when a suitable mechanical force is applied.Exemplary separable coupling elements include male and female elements,such as a rod and tube which may be axially separated, a tab andreceptacle which may be radially separated, and the like.

In a specific embodiment of the catheter, the catheter body may comprisean expansion element, such as an inflatable balloon, near its distalend. The expansion element will be positionable distal to theretractable sheath so that it can be used to regularly expand one ormore of the prostheses. For example, the inflatable balloon may have alubricious outer surface and carry multiple prostheses on its outersurface so that sheath retraction can expose one, two, three, or more ofthe prostheses. The remaining prostheses will continue to be covered bythe sheath. When inflating the balloon, however, only that portion ofthe balloon and those prostheses carried on the exposed portion of theballoon will be inflated. The remaining (proximal) portion of theballoon will continue to be constrained by the sheath so that neitherthe balloon nor the prostheses covered by the sheath will be expanded.In this way, any preselected number of the individual prostheses may beexpanded at one time, while the remaining prostheses are protected andunexpanded, remaining available for subsequent expansion using theballoon.

Alternatively or in addition to the balloon, the catheter body maycomprise a heater for selectively heating prostheses which have beenadvanced distally beyond the sheath. For example, the catheter body mayhave a lumen for delivering a heated medium, such as heated saline,intravascularly to heat and expand stents or other prostheses formedfrom suitable heat memory alloys (as described in more detail below).Alternatively, a separate exterior guide catheter or other tube may beused for delivering such a heated medium to effect expansion of theprostheses. As a third alternative, a powered heating element, such as aradio frequency heater, electrical resistance heater, or laser-heatedelement, may be provided on the catheter body for directly heating theexposed prostheses.

For the delivery of individual prostheses or stents which are joined byfrangible or breakable links, as discussed above, it will often bedesirable to provide a shearing mechanism on the catheter. The shearingmechanism will usually be mechanical, but could also be electrolytic,ultrasonic, or chemical. In the exemplary embodiments, the shearingmechanism comprises a first shearing element on a distal region of thecatheter body and a second or mating shearing element on a distal regionof the sheath. The prostheses may be advanced from the sheath while theshearing mechanism on the catheter body is distally advanced (leaving aspace or opening for prosthesis deployment). After a desired number ofprostheses have been deployed, the catheter body may be retractedrelative to the sheath in order to close the shearing elements to severthe link(s) between the advanced prostheses and those prostheses whichremain within the sheath. In other cases, the shearing mechanism couldbe an electrode for inducing electrolytic breakage of the link, anultrasonic transducer for mechanically degrading a susceptible link(i.e. a link having a resonant frequency which corresponds to theultrasonic transducer), a luminal port for releasing a chemical agentselected to chemically degrade the link, or the like.

In a further alternative embodiment, a catheter constructed inaccordance with the principles of the present invention comprises apusher tube, a plurality of radially expansible prostheses arrangedend-to-end and extending distally of the distal end of the pusher tube,and a sheath disposed coaxially over the pusher tube and the prostheses.Optionally, but not necessarily, this embodiment will include a catheterbody disposed coaxially within the pusher tube and prostheses. Byretracting the sheath proximally relative to the pusher tube, individualones or groups of the prostheses will be exposed and deployed. Thecatheter body may be used in any of the ways described previously inorder to effect or control deployment of the prostheses. Optionally, thepusher tube, the sheath, or both, may have a greater column strengththan the catheter body when the catheter body is employed.

Systems of detachable expansible prostheses according to the presentinvention include a plurality of ring-like radially expansibleprostheses arranged end-to-end along an elongate axis. At least one pairof coupling elements join each pair of adjacent prostheses, where thecoupling elements physically separate without fracture in response toaxial tension or differential radial expansion. The coupling elements,however, remain coupled when subjected to axial compression such as mayoccur as the prostheses are axially advanced within a body lumen orelsewhere. The prostheses may be composed of a malleable material sothat they will be expansible in response to an internally appliedradially expansive force, such as a balloon expansion force applied by aballoon carried by the catheter body in any of the prior embodiments ofthe present invention. Alternatively, the prostheses may be composed ofa resilient material, such as spring stainless steel, nickel-titaniumalloy; or the like, so that they may be “self-expanding,” i.e. expandwhen released from radial constraint. As a third alternative, theprostheses may be composed of a heat memory alloy, such as a nickeltitanium alloy, so that they may be induced to expand upon exposure to atemperature above body temperature. Materials suitable for forming eachof these three types of prostheses are well described in the patent andmedical literature.

In specific examples of the systems, the coupling elements may be maleand female so that they decouple upon the application of an axial force.For example, the coupling elements may be a rod and a tube having acentral passageway for receiving the rod. Alternatively, the couplingelements may be configured to decouple upon differential radialexpansion. For example, a first coupling element may extend from the endof a first prostheses and have an enlarged portion or end. By providinga cut-out in the adjacent prostheses having a periphery which matchesthe periphery of the extension on the first prostheses, couplingelements can be mated and locked together. The locking will resist axialseparation, but permit radial separation when one of the prostheses isradially expanded.

The systems of prostheses just described may be preferably employed withany of the catheter delivery systems described previously.

The present invention further provides methods for stenting extendedlengths of the body lumen, where the methods comprise introducing acatheter carrying a plurality of radially expansible prostheses to atarget site within the body lumen. The prostheses are arrangedend-to-end and are covered by a sheath. The prostheses are then deployedby retracting the sheath relative to the prostheses by a firstpreselected distance to uncover a first predetermined number of theprostheses. After retraction of the sheath, a first predetermined numberof prostheses, which may be anywhere from one up to the entire number ofprostheses being carried, are radially expanded at the target sitewithin the target site of the body lumen.

Prosthesis expansion may be achieved in a variety of ways. In a firstinstance, the prostheses are expanded by inflating a balloon within theparticular prosthesis to be expanded. For example, a single balloon maybe disposed under all the prostheses, with the sheath retracted toexpose only those prostheses to be deployed. When the balloon isexpanded, the balloon will expand the exposed prostheses, with expansionof the prostheses which remain covered being restrained by the sheath.By further retracting the sheath, the previously undeployed prosthesesmay then be deployed. Optionally, the prostheses are advanced (or atleast axially restrained relative to the sheath) by a pusher tube whichengages a proximal end of the proximal-most prosthesis.

As an alternative to balloon expansion, the uncovered prostheses may beexpanded by exposure to heat. The heat may be applied by directing aheated medium to the prostheses, directing electrical energy through theprostheses, and/or energizing a heating element positioned adjacent tothe uncovered prostheses.

In preferred aspects of the methods of the present invention, the bodylumen will be a blood vessel, preferably a coronary artery, a cerebralartery, or other small artery. The prostheses will preferably be coatedwith biologically active or inert agent, such as an agent selected toinhibit hyperplasia, more specifically being any of the particularagents set forth hereinabove.

The catheters of the present invention will comprise a number of coaxialcomponents, such as sheaths, pusher tubes, catheter bodies, and thelike. While it will often be described that stents or other prosthesesare advanced distally from the sheath, such description will apply tosheaths which are retracted proximally relative to the prostheses toeffect the release. Thus, all descriptions of direction are meant to berelative.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view illustrating a stent delivery catheterconstructed in accordance with the principles of the present invention.

FIG. 2 is a detailed view of the distal end of the catheter of FIG. 1with portions broken away.

FIGS. 3A-3F illustrate use of the catheter of FIG. 1 for deploying aplurality of stents using balloon expansion.

FIG. 4 illustrates an exemplary prosthesis constructed in accordancewith the principles of the present invention.

FIGS. 5A and 5B illustrate a prosthesis similar to that shown in FIG. 4,but further including coupling elements for permitting detachablecoupling of adjacent prostheses.

FIG. 5C illustrates a pair of prostheses, as shown in FIGS. 5A and FIG.5B, joined together by the coupling elements.

FIG. 5D illustrates a pair of adjacent prostheses coupled by a modifiedcoupling element.

FIGS. 5E and 5F illustrate radial separation of the adjacent prosthesesof FIG. 5C.

FIGS. 6A and 6B illustrate a second coupling mechanism constructed inaccordance with the principles of the present invention.

FIG. 7 illustrates a frangible linkage for joining a pair of adjacentprostheses.

FIGS. 8A-8C illustrate a catheter and its use for deliveringself-expanding prostheses according to the methods of the presentinvention.

FIGS. 9A and 9C illustrate an alternative catheter construction intendedfor delivering self-expanding prostheses according to the methods of thepresent invention.

FIGS. 10A-10C illustrates use of the catheter for delivering prosthesesby a heat-induction method in accordance with the principles of thepresent invention.

FIG. 11 illustrates an alternative catheter construction for deliveringmultiple prostheses via a heat-induction protocol in accordance with theprinciples of the present invention.

FIGS. 12A-12D illustrate a catheter for delivering multiple prosthesesusing balloon expansion in accordance with the methods of the presentinvention.

FIGS. 13A-13D illustrate a catheter including a stent valve fordelivering multiple prostheses using balloon expansion in accordancewith the methods of the present invention.

FIG. 14 illustrates an exemplary kit constructed in accordance with theprinciples of the present invention.

DETAILED DESCRIPTION OF THE SPECIFIC EMBODIMENTS

Referring now to FIG. 1, the stent delivery catheter 10 comprises acatheter body 12 having a proximal end 14 and a distal end 16. Thecatheter body is formed from a conventional catheter material, such asbraided or coiled stainless steel, a natural or synthetic polymer,including silicone rubber, polyethylene, polyvinylchloride,polyurethane, polyester, polytetrafluoroethylene, nylon, and the like.The body may be formed as a composite having one or more reinforcementlayers incorporated within a polymeric shell in order to enhancestrength, flexibility, and toughness. For intravascular use, thecatheter body will typically have a length in the range from 40 cm to150 cm, usually being between 40 cm and 120 cm for peripheral bloodvessels and between 110 cm and 150 cm for coronary arteries. The outerdiameter of the catheter body may vary depending on the intended use,typically being between 3 French and 15 French, usually from 5 French to9 French.

Catheter 10 will include a handle 18 at its proximal end 14. The handlemay include a guidewire port 20 and a balloon inflation port 22, as wellas a handle grip 24 which advances a pusher shaft whose distal end 26 isshown in FIG. 2. Additionally, the handle permits reciprocation of acatheter delivery balloon 28, also shown in FIG. 2.

A plurality of stents 30 are carried in a lumen of the catheter body 12,as shown in FIG. 2. While three stents 30 are shown, it will beappreciated that additional stents may be carried generally within theranges disclosed above. The illustrated stents comprise a plurality ofserpentine ring structures joined by offset struts. It will beappreciated, however, that a wide variety of stent structures could becarried by the catheter 10, generally as described above.

Referring now to FIGS. 3A-3F, the distal end 16 of the catheter 10 isadvanced to target location 40 within a diseased blood vessel (BV) overa guidewire 42, as illustrated in FIG. 3B. Balloon 28 carries a first ofthe three stents 30, and is advanced distally from the catheter todeploy the stent within the treatment region 40, as illustrated in FIG.3B (optionally by retracting the catheter body 12 proximally relative toballoon 28). Once the stent 30 is properly located, the balloon 28 isinflated to deploy the stent (and optionally dilate the treatmentregion), as illustrated in FIG. 3C.

The balloon is then deflated, and retracted back into the distal end ofthe catheter 16, as illustrated in FIG. 3D. The expanded stent is leftin place. The balloon 28 is retracted back to within the second stent30, as illustrated in FIG. 3E. The second stent has been advanced usingthe pusher 26 so that it is properly located over the balloon 28, andthe distal end of the catheter 16 may then be advanced so that thesecond stent 30 is located within a second treatment region spaced apartfrom the first treatment region. As illustrated in FIG. 3F, thetreatment regions are adjacent to each other. It will be appreciated,however, that the second treatment region could be spaced a substantialdistance from the first treatment region. Deployment of the second stent30 is then completed in the same manner as described above for the firststent. Similarly, deployment of third, fourth, fifth, and additionalstents 30 may be effected in the same manner. In this way, it will beappreciated that relatively lengthy and/or disseminated regions within ablood vessel may be treated.

Referring now to FIG. 4, an exemplary prosthesis 50 constructed inaccordance with the principles of the present invention is illustrated.The prosthesis has a tubular body 52 having a plurality of axial slots54, typically formed by laser cutting or chemical etching a tubularstock, such as stainless steel or nickel-titanium hypotube. Prosthesis50, which may be delivered in groups of two, three, four, or more inaccordance with the principles of the present invention, will have alength within the ranges set forth above. The diameter, prior toexpansion, will typically be below 2 mm, preferably being below 1 mm,although in some instances much larger diameters can be used. Thediameter of the prosthesis 50 upon expansion, of course, will be muchgreater, typically being at least twice as large, sometimes being atleast three times as large, or even larger.

Referring now to FIGS. 5A and 5B, a prosthesis 60, similar to prosthesis50, includes a pair of coupling elements 62 which are received in matingslots 64. FIG. 5B is a “rolled-out” view of the “rolled-out” view of theprosthesis 60 for better illustrating the coupling element 62 and slots64 of the prosthesis 60.

As shown in FIG. 5C, pairs of prosthesis 60 may be joined or coupled bycircumferentially aligning the coupling element 62 with the slot 64.Although only a single coupling element 62 and slot 64 is visible inFIG. 5C, it will be appreciated that the second coupling element andslot will be located on the opposite side of the illustrated pair ofprostheses.

In FIG. 5C, the two prosthesis 60 are abutted directly against eachother. Such a configuration is advantageous in that it provides for asubstantially continuous stent or graft structure when the pair isexpanded together in a body lumen. The structure, however, isdisadvantageous in that it does not provide for flexibility at the pointwhere the two prostheses meet. In order to provide for greaterflexibility, as shown in FIG. 5D, a coupling element 62′ can have anelongated shank to provide for a desired offset, typically in the rangefrom 0.05 mm to 1 mm, preferably from 0.1 mm to 0.5 mm.

Referring now to FIGS. 5E and 5F, axial separation of the prostheses 60is achieved by differential radial expansion of at least one of theprostheses. For example, when both prostheses 60 are in their unexpandedconfigurations, as shown in FIG. 5E, the coupling elements 62 areconstrained by the slots 64, as previously described. By radiallyexpanding the left-hand prostheses 60, as shown in FIG. 5F, the couplingelements 62 will be moved radially outwardly from the slots so that thetwo prostheses are no longer axially linked. It will be appreciated,however, that the two prostheses 60 may be radially expanded together(as described in more detail hereinafter) in a manner which preservesthe link created by the coupling elements 62 and slots 64 so thatcombinations of two, three, four, or more prostheses may be deliveredsimultaneously and, in effect, provide a continuous prosthesis having alength which is some multiple of the length of each individualprostheses 60. The combined prostheses may then be separated from anyadditional prostheses (which remain in a delivery catheter as describedbelow) by the radial expansion of those prostheses which are to bedeployed. In this way, stents, grafts, or other prostheses may bedelivered to the body lumen in both different lengths (by properlyselecting the number of individual prostheses 60) and at differentlocations (by releasing individual or multiple prostheses 60 atdifferent portions of the body lumen).

Axially separable coupling elements may also be provided, as illustratedin FIGS. 6A and 6B. Each prosthesis 70 includes a pair of male couplingelements 72 at one end and a pair of female coupling elements 74 at theother end. The male coupling elements 72 are typically short rods whichextend axially from the periphery of the prosthesis end and the femalecoupling elements are typically short tubes having hollow interiorswhich detachably receive the male coupling elements. Thus, theprostheses 70 may be joined in an end-to-end manner, as shown in FIG.6B. The prostheses are separated by pulling them in an axial direction,as shown by arrow 76, but will remain linked under axial compression aswell as when exposed to a substantial bending moment. Thus, the axiallyseparable coupling structures of FIGS. 6A and 6B are advantageous inthat they remain linked during deployment of the prostheses 70, evenwhen deployment involves significant bending and radial stress.Separation may be effected by pullback on the delivery catheter in orderto disengage the coupling elements 72 and 74.

A third approach for detachably coupling adjacent prostheses 80 isillustrated in FIG. 7. Each prosthesis 80 comprises an expansible ringof diamond-shaped members. Other conventional stent or prosthesesstructures, however, could also be used. The adjacent prostheses 80 arejoined by an axial beam 82 which preferably includes a weakened segment84 near its midpoint. The use of such a joining structure, which willrequire physical breakage (as opposed to the simple detachmentcharacteristic of the embodiment of FIGS. 5 and 6) is advantageous inthat it provides a very strong linkage which permits both theapplication of axial compression and axial tension without decoupling.The disadvantage of such a linkage is that it usually requires somemechanism or capability to be incorporated in the delivery catheter topermit selective breakage of the couple.

Referring now to FIGS. 8A-8C, a catheter 100 suitable for delivering aplurality of self-expanding prostheses 102 will be described. Catheter100 comprises a sheath 104 having an axial lumen which carries theprostheses 102 near its distal end 106. A pusher tube 108 is alsopositioned in the lumen and is located proximally of the proximal mostprosthesis 102. The individual prostheses 102 may be delivered into abody lumen, typically a blood vessel BV, as illustrated in FIG. 8B. Thecatheter is introduced over a guidewire GW to a desired target site inthe blood vessel BV. When at the target site, a first of the prostheses102 is deployed by axially advancing the pusher tube 104 so that theline of prostheses 102 is axially advanced, with the distal-mostprostheses being released from the distal end 106 of the catheter. As itis released, the distal-most prostheses 102 expands since it is beingreleased from the radial constraint provided by the sheath 104.

Catheter 100 of FIGS. 8A-8C is intended for delivering prostheses whichabut each other in an end-to-end manner, but which are otherwiseunconnected. A catheter 120 intended for releasing self-expandingprostheses 122 which are mechanically linked by frangible couplingelements 124 is illustrated in FIGS. 9A-9C. The prostheses 122 andcoupling elements 124 may be similar to the prosthesis structure shownin FIG. 7, or may comprise other linked prosthesis or stent structures,for example as shown in U.S. Pat. No. 6,258,117, the disclosure of whichis incorporated herein by reference.

Catheter 120 comprises a sheath 126, a pusher tube 128, and a catheterbody 130 having a shearing element 132 at its distal end. Conveniently,the pusher tube 128 is coaxially received over a shaft 134 of thecatheter body 130. In this way, the pusher tube may be used to axiallyadvance each prosthesis 122 by pushing on the proximal end of theproximal-most prosthesis, as shown in FIG. 9B.

The catheter 120 is advanced over a guidewire GW to a desired targetsite in a blood vessel BV. After reaching the target site, at least afirst prosthesis 122 is advanced from the distal end of the sheath sothat it radially expands to engage an inner wall of the blood vessel.After the at least one prosthesis 122 is advanced sufficiently far, thefrangible coupling elements 124 will reach a shearing element 136,typically a metal ring, disposed at the distal end of the sheath 126. Bythen axially retracting the catheter body 130, a chamfered surface 138of the shearing element 132 is engaged against the shearing element 136in order to shear the links 122, releasing the prosthesis 122, asillustrated in FIG. 9C. After deployment and release of the firstprosthesis 122, additional prosthesis 122 may be released adjacent tothe first prosthesis or at different, axially spaced-apart locationswithin the blood vessel.

Referring now to FIGS. 10A-10C, a catheter 140 for delivering aplurality of heat expansible prostheses 142 is illustrated. Theprostheses 142 are composed of a heat memory alloy, such as a nickeltitanium alloy, which has been programmed to remain in an unexpandedconfiguration when maintained at body temperature or below, and toassume an expanded configuration when exposed to temperatures above bodytemperature, typically temperatures above 43° C., often above 45° C. Theprostheses will have coupling members which anchor successive prostheses142 together, typically the radially separating anchors illustrated inFIGS. 5A-5F.

The catheter 140 includes a sheath 144 and a pusher tube 146. Thecatheter 140 is advanced to a desired target site within the bloodvessel BV over a guidewire GW in a conventional manner. After thedistal-most prostheses 142 has been fully advanced from the sheath 144(usually by retracting the sheath 144 while the prostheses are heldstationary relative to the blood vessel BV using the pusher tube 146),as shown in FIG. 10B, it will remain both unexpanded and attached to thenext proximal prosthesis 142 which remains within the sheath. It isimportant that the advanced prosthesis 142 be anchored or tethered tothe remaining prostheses since it has not yet been expanded and it wouldotherwise be lost into the lumen of the blood vessel.

After the uncovered prostheses is properly positioned, a heated mediummay be introduced through a lumen of the catheter body 148 so that itflows outwardly through the interior of the distal-most prosthesis 142.By properly selecting the temperature of the heated medium, theprosthesis to be deployed can be heated sufficiently to induce radialexpansion, as illustrated in FIG. 10C. By positioning the catheter body148 so that its distal tip is coterminous with the distal tip of thesheath 144, inadvertent heating of the prostheses 142 which remainwithin the sheath can be avoided. After the prosthesis 142 has radiallyexpanded, it will separate from the coupling elements 148 located on thenext prosthesis which remains within the sheath 144. Additional ones orgroups of prostheses 142 may then be deployed, either at the same targetsite or at a different target site axially spaced-apart within the lumenof the blood vessel BV.

As illustrated in FIG. 11, instead of using an internal catheter body148, as illustrated in FIGS. 10A-10C, an external sheath 150 may be usedto deliver the heated medium around one or more deployed prostheses 142.Other aspects of the construction of catheter 140 may remain the same.Optionally, if prosthesis is martensitic at body temperature, furtherradial expansion can be achieved by internal balloon expansion.

Referring now to FIGS. 12A-12D, catheter 160 intended for delivery ofmultiple prostheses 162 by balloon deployment is illustrated. Catheter160 comprises a sheath 164, pusher tube 166, and a catheter body 168.The catheter body 168 includes an expansible balloon 170 over its distalportion. Individual prostheses 162 are deployed, as illustrated in FIGS.12B and 12C, by crossing the target area with catheter 160 and thenretracting sheath 164. A distal portion of the balloon 170 lies withinthe distal-most deployed prosthesis 162, as shown in FIG. 12B. Theremaining proximal portion of the balloon 170 will, of course, remainwithin the other prostheses 162 which themselves remain within thesheath 164. The balloon 170 is then inflated, but only the distalportion of the balloon beyond the sheath inflates within the distalprosthesis 162, as illustrated in FIG. 12C. Expansion of the remainingproximal portion of the balloon is prevented by the sheath 164.Similarly, the remaining prostheses 162 remain unexpanded since theyremain within the sheath 164. After deployment of prostheses 162,balloon 170 may be deflated and retracted into sheath 164 and remainingprostheses 162.

Referring now to FIG. 12D, additional prostheses 162 may be deployed,either at the same target location within the blood vessel or at adifferent, spaced-apart locations within the blood vessel. Deployment oftwo prostheses 162 is illustrated. The two prostheses 162 are axiallyexposed as the sheath is retracted over the stents which are positionedover the uninflated balloon 170. The balloon 170 is then inflated, asillustrated in FIG. 12D, thus expanding the prostheses 162 within theblood vessel BV. It will be appreciated that the catheter 160 couldcarry many more than the four illustrated prostheses 162, and three,four, five, ten, and even 20 or more individual prostheses could bedeployed at one time, with additional single prostheses or groups ofprostheses being deployed at different times and/or at differentlocations within the blood vessel.

Referring now to FIGS. 13A-13D, another embodiment of a catheter 180intended for delivery of multiple prostheses 182 by balloon deploymentis illustrated. In this embodiment, catheter 180 comprises a sheath 184having a valve member 185 at its distal end, a pusher tube 186, and acatheter body 188. The catheter body 188 includes an expansible balloon190 over its distal portion. To deploy prostheses 182, as illustrated inFIG. 13B, a predetermined number of prostheses 182 is first exposed byretracting sheath 184 proximally (arrows) while holding pusher tube 186in place. As shown in FIGS. 13B and 13C, valve member 185 may be used toengage a distal end of one of the prostheses 182 and the sheath 184 andthe pusher tube may be retracted proximally together (arrows in FIG.13C) to separate a proximal number of prostheses 182 from a distalnumber of prostheses 182. The distal portion of the balloon 190 lieswithin the distal, deployed prostheses 182. The remaining proximalportion of the balloon 190 will remain within the other prostheses 182which themselves remain within the sheath 184. The balloon 190 is theninflated, as shown in FIG. 13D, but only the distal portion of theballoon inflates within the distal prostheses 182, as illustrated inFIG. 12C. Expansion of the remaining proximal portion of the balloon isprevented by the sheath 184. Similarly, the remaining prostheses 182remain unexpanded since they remain within the sheath 184.

Referring now to FIG. 13D, single or multiple prostheses 182 may bedeployed at the same target location within the blood vessel. Additionalprostheses 182 may also be deployed at different, spaced-apart locationswithin the blood vessel. Deployment of two prostheses 182 is illustratedat one location in FIG. 13D. It will be appreciated that the catheter180 could carry many more than the four illustrated prostheses 182, andthree, four, five, ten, and even 20 or more individual prostheses couldbe deployed at one time, with additional single prostheses or groups ofprostheses being deployed at different times and/or at differentlocations within the blood vessel.

Referring now to FIG. 14, kits 200 according to the present inventioncomprise a catheter 160 (or any other of the illustrated catheters ofthe present invention) in combination with instructions for use IFU. Theinstructions for use set forth any of the methods of the presentinvention, and in particular set forth how the catheter 180 may be usedto implant single or multiple prostheses within a blood vessel or otherbody lumen. The catheter 180 and instructions for use will typically bepackaged together, for example within a conventional package 202, suchas a box, tube, pouch, tray, or the like. Catheter 160 will typically bemaintained in a sterile condition within the package 202. Theinstructions for use may be provided on a package insert, may be printedin whole or in part on the packaging, or may be provided in other ways,such as electronically over the internet, on an electronic medium, suchas a CD, DVD, or the like.

The preferred embodiments of the invention are described above in detailfor the purpose of setting forth a complete disclosure and for the sakeof explanation and clarity. Those skilled in the art will envision othermodifications within the scope and sprit of the present disclosure.

1 A method for stenting extended lengths of a body lumen, said methodcomprising: introducing a catheter carrying a plurality of radiallyexpansible prostheses to a stenotic lesion within the body lumen,wherein the prostheses are arranged end-to-end on an expandable member;radially expanding at least some of the plurality of prosthesessimultaneously at a first location within the stenotic lesion, whereinthe expanded prostheses have a combined length of between 40 mm to 100mm and engage a wall of the body lumen with sufficient radial force tomaintain patency thereof, the expanded prostheses being spaced apartfrom each other after expansion by a distance no more than about 1 mm soas to inhibit hyperplasia therebetween.
 2. A method as in claim 1,wherein a sheath covers at least some of the plurality of prostheses,the method further comprising retracting a sheath by a first distance touncover the prostheses for radial expansion and wherein the uncoveredprostheses do not expand during retraction of the sheath.
 3. A method asin claim 1, wherein at least one other prosthesis remains on thecatheter in the unexpanded configuration while the prostheses areradially expanded.
 4. A method as in claim 1, wherein the expandablemember comprises a balloon and radially expanding comprises inflatingthe balloon.
 5. A method as in claim 2, wherein the expandable membercomprises a balloon and the balloon is disposed under the prostheses tobe radially expanded and at least another prosthesis, and whereinexpansion of the at least another prosthesis is constrained by thesheath when the expandable member is expanded.
 6. A method as in claim2, further comprising engaging a proximal end of the plurality ofprostheses with a pusher tube to restrain axial movement thereof as thesheath is retracted.
 7. A method as in claim 2, further comprisingengaging at least one of the plurality of prostheses with a valve memberdisposed near a distal end of the sheath.
 8. A method as in claim 6,further comprising retracting the pusher tube along with the sheath inorder to separate the prostheses to be expanded from any remainingprostheses on the delivery catheter.
 9. A method as in claim 1, furthercomprising heating the uncovered prostheses to effect expansion thereof.10. A method as in claim 1, wherein the prostheses are balloonexpandable.
 11. A method as in claim 1, wherein the plurality ofprostheses are resilient and radially constrained by a sheath disposedat least partially thereover, wherein the prostheses radiallyself-expand as the sheath is retracted.
 12. A method as in claim 1,further comprising repositioning the catheter and further expandingadditional prostheses at a second location within the stenotic lesion.13. A method as in claim 1, wherein the body lumen is a blood vessel.14. A method as in claim 1, wherein the prostheses releasably carry atleast one agent disposed thereon.
 15. A method as in claim 14, whereinthe agent inhibits hyperplasia.
 16. A method as in claim 1, furthercomprising dilating the radially expanded prostheses with the expandablemember after expansion thereof.
 17. A catheter for stenting extendedlengths of a body lumen, said catheter comprising: a catheter bodyhaving a proximal end and a distal end; at least three discrete stentscarried near a distal end of the catheter body, the discrete stentsradially expandable from a contracted configuration to an expandedconfiguration in which the stents engage a wall of the body lumen; adeployment mechanism for selectively deploying the stents bothindependently and in groups from the catheter body within the bodylumen, the deployment mechanism being adapted to deploy a multiplicityof stents while at least one other stent is retained in the catheterunconnected to the multiplicity after the multiplicity of stents arereleased from the catheter and are in the expanded configuration,wherein the deployment mechanism allows the multiplicity of stents toradially expand into the expanded configuration with a distance betweenadjacent stents small enough to inhibit hyperplasia therebetween.
 18. Acatheter as in claim 17, wherein the catheter body is free of fixedstructures intervening between the stents
 19. A catheter as in claim 17,comprising at least four discrete stents carried near the distal end ofthe catheter body.
 20. A catheter as in claim 19, comprising at leastfive discrete stents carried near the distal end of the catheter body.21. A catheter as in claim 17, wherein the deploying means comprises atleast three independently inflatable balloons, wherein each ballooncarries at least one stent.
 22. A catheter as in claim 17, wherein thedeploying mechanism comprises a single balloon reciprocatably mountedwithin the catheter body and a pusher for successively loading stentsover the balloon.
 23. A catheter as in claim 17, wherein the deployingmechanism comprises a radial restraint which holds the stents in aradially collapsed configuration and which can be selectively retractedto release the stents independently or in groups.
 24. A catheter as inclaim 17, wherein the deploying mechanism comprises a radial restraintwhich holds the stents in a radially collapsed configuration and apusher for holding the stents in place while the radial restraint isretracted to expose the stents from the distal end of the catheter bodyindependently or in groups.
 25. A catheter as in claim 24, wherein theradial restraint comprises a sheath having a valve member at its distalend for engaging a proximal stent to separate the proximal stent from adistal stent.
 26. A catheter as in claim 17, wherein the stents have atleast one agent disposed thereon.
 27. A catheter as in claim 26, whereinthe agent is disposed in a bioresorbable material formed on or withinthe prostheses.
 28. A catheter as in claim 27, wherein the bioresorbablematerial is selected from the group consisting of polyethylene glycol,collagen, gelatin, polyglycolic acids, and polylactic acids.
 29. Acatheter as in claim 26, wherein the agent inhibits hyperplasia.
 30. Acatheter as in claim 29, wherein the agent is biologically active.
 31. Acatheter as in claim 17, wherein the biologically active agent isselected from the group consisting of anti-neoplastic drugs such aspaclitaxel, methotrexate, and batimastal; antibiotics such asdoxycycline, tetracycline, rapamycin, and actinomycin;immunosuppressants such as dexamethosone and methyl prednisolone; nitricoxide sources such as nitroprussides; estrogen; and estradiols.
 32. Acatheter as in claim 29, wherein the agent is biologically inert.
 33. Acatheter as in claim 32, wherein the biologically inert agent isselected from the group consisting of collagen, PEG, PGA, ceramicmaterial, platinum and gold.
 34. A catheter as in claim 17, wherein thestents are composed at least partly of a bioabsorbable material.
 35. Acatheter as in claim 34, wherein a bioactive substance is disposed inthe bioabsorbable material and is released over time as the materialdegrades.
 36. A catheter as in claim 34, wherein the bioabsorbablematerial is formed on or within a scaffold composed of anon-bioabsorbable material.
 37. The catheter of claim 17, wherein thedeployment mechanism allows the stents to expand such that the distancebetween the adjacent stents after expansion is no more than about 1 mm.38. A catheter system for implanting prostheses in a body lumen, saidcatheter system comprising: a catheter body having a proximal end and adistal end; at least two radially expandable prostheses carried near adistal end of the catheter body, the at least two prostheses radiallyexpandable from a contracted configuration to an expanded configurationin which the prostheses engage a wall of the body lumen, the at leasttwo prostheses being independently deployable of one another; and anexpansion element disposed near the distal end of the catheter bodyhaving an expandable portion adapted to radially expand one or more ofthe at least two prostheses into engagement with a wall of the bodylumen, the expandable portion having an expandable length which isoperator-adjustable from the proximal end such that expanded length maybe expanded while a remaining length of the expansion element remainsunexpanded; wherein at least two prostheses are positionable on theexpandable portion so as to be expanded simultaneously, and wherein atleast one of the prostheses may be retained unexpanded on the catheterwhile at least one other of the prostheses is being expanded.
 39. Thecatheter system of claim 38, wherein the expansion element comprises aninflatable balloon.
 40. The catheter system of claim 38, furthercomprising a sheath axially movable on the catheter body to cover atleast a portion of the expansion element and the prostheses.
 41. Thecatheter system of claim 40, wherein the sheath is adapted to constrainexpansion of a selected length of the expansion element.
 42. Thecatheter system of claim 40, further comprising a valve member coupledto the sheath and adapted to engage one or more of the prostheses. 43.The catheter system of claim 40, further comprising a pusher axiallymovable relative to the sheath and adapted to hold the prostheses inposition as the sheath is moved.
 44. The catheter system of claim 43,wherein the pusher may be selectively coupled and uncoupled with thesheath so as to move axially therewith or to stay fixed as the sheathmoves.
 45. The catheter system of claim 38, wherein the prostheses areunconnected to each other prior to deployment.
 46. The catheter systemof claim 38, wherein the expansion element has a length at least as longas the combined length of two of the prostheses.
 47. The catheter systemof claim 38, wherein at least three prostheses are carried by thecatheter.
 48. The catheter system of claim 47, wherein the expandableportion of the expansion element has a maximum length at least as longas the combined length of all of the prostheses in the catheter.
 49. Thecatheter system of claim 38, wherein the prostheses comprise vascularstents.
 50. The catheter of claim 49, wherein the prostheses carry atherapeutic agent.
 51. The catheter system of claim 50, wherein thetherapeutic agent inhibits hyperplasia.
 52. The catheter system of claim50, wherein the therapeutic agent is disposed in a bioresorbablematerial formed on or within the prostheses.
 53. A catheter system as inclaim 52, wherein the bioresorbable material is selected from the groupconsisting of polyethylene glycol, collagen, gelatin polyglycolic acids,and polylactic acids.
 54. The catheter system of claim 52, wherein thebioresorbable material is coated on the prosthesis.
 55. The cathetersystem of claim 38, wherein the prostheses are adapted to expand suchthat adjacent ends of thereof are no more than about 1 mm apart.
 56. Thecatheter system of claim 38, wherein following expansion in the bodylumen the prostheses are substantially free of material extendingbetween adjacent prostheses.